Small circuit breaker having large contact separation

ABSTRACT

A compact molded case circuit breaker is provided with a springpowered overcenter toggle-type contact operating mechanism so constructed that initial closing movement of the movable contact is a result of a force transmitted directly from the manual operating handle. The contact operating mechanism also provides a movable stop that permits an exceptionally large contact separation during automatic tripping, and during normal manual opening there is a much smaller contact separation.

United States Patent 1191 0 r 14 1 Nov. 19, 1974 [54] SMALL CIRCUIT BREAKER HAVING 3.599.130 8/1971 Murai et al. 335/174 LARGE CONTACT SEPARATION Primary ExaminerHarold Broome [75] Inventor i Omss Bramalea Attorney, Agent, or Firm-Ostrolenk, Faber, Gerb &

Ontario, Canada Soffen [73] Assignee: ITE Circuit Breaker (Canada) Limited, Weston, Ontario, Canada [57] ABSTRACT [22] Filed: Dec. 4, 1973 A compact molded case circuit breaker is provided with a spring-powered overcenter toggle-type contact [21] Appl' 421533 operating mechanism so constructed that initial closing movement of the movable contact is a result of a [52] US. Cl. 335/174, 335/21 force ansmitted directly from the manual operating [51] Int. Cl. IIOlh 71/10 handle- The ontact operating mechanism also pro- [58] Field of Search 335/174, 43, 14, 21 vides a movable stop that permits an exceptionally large contact separation during automatic tripping,

[56] References Cited and during normal manual opening there is a much UNTED STATES PATENTS smaller contact separation.

3,475.711 10/1969 Stokes 335/43 7 Claims, 4 Drawing Figures PATENmrznv 19mm SHEEI 2 OF 4 PATENI L am x 91974 saw u or 4 SMALL CIRCUIT BREAKER HAVING LARGE CONTACT SEPARATION This invention relates to circuit breakers in general, and more particularly relates to small circuit breakers having relatively large contact separation in the open circuit position.

Molded case circuit breakers for home and light industrial applications are usually very compact structures having many relatively moving mechanical elements confined within a very small area. The contact operating mechanisms of such circuit breakers must be trip free and are usually of the spring-powered overcenter type.

The instant invention provides relatively large contact separation in a circuit breaker of this type, but is still able to utilize a very compact contact operating mechanism by constructing the latter so that on contact closing there is no need to rely solely on spring biasing forces that are repositioned by overcentering a toggle mechanism. Instead, in accordance with the instant invention, initial closing movement of the movable contact arm is achieved by positive mechanical action, transmitting force directly from the manual operating handle to the movable contact arm. This movement of the movable contact arm contributes to achieving an overcenter condition of the toggle mechanism, and as this is occurring the manual operating handle is also repositioning the main operating spring to an overcenter position, with this overcenter position being reached before the circuit breaker contacts engage so that during the last portion of the closing stroke the main spring provides the entire closing force.

Circuit breakers of the type under consideration are also provided with means for automatically tripping the breaker under overload and short circuit conditions.

During automatic tripping, arcing conditions between the parting contacts are more severe than during manual opening. Since increased contact separation facilitates arc interruption, it is desirable and often necessary to have a large contact separation. However, with a large contact separation, the large contact travel during closing results in the development of large mechanical forces which produce excessive noise and may ultimately damage the breaker after many operations thereof. Thus, in accordance with the instant invention, when infrequent automatic tripping takes place there is an exceptionally large contact separation, and during much more frequent manual opening there is a significantly smaller contact separation.

Accordingly, a primary object of the instant invention is to provide a novel construction for a relatively compact molded case circuit breaker.

Another object is to provide a circuit breaker of this type having relatively large contact separation and having a contact operating mechanism so constructed that during closing initial movement of the movable contact arm results from a positive mechanical connection to the manual operating handle.

A further object is to provide a circuit breaker of this type-in which there is an exceptionally large contact separation for automatic tripping conditions and a much smaller contact separation during normal manual operation.

These objects as well as other objects of this invention will become readily apparent after reading the following description of the accompanying drawings in which:

FIGS. I-3 are side elevations of a molded case circuit breaker constructed in accordance with teachings of the instant invention, with the near wall of the housing removed to reveal the internal elements of the circuit breaker. In FIG. I the circuit breaker contacts are closed, in FIG. 2 the circuit breaker is in the manual OFF position with the contact operating mechanism in reset position. and in FIG. 3 the circuit breaker is tripped open.

FIG. 4 is an exploded perspective of the circuit breaker electrical and mechanical operating elements.

Now referring to the figures. Circuit breaker H0 is of the type described in US. Pat. No. 3,147,353 issued Sept. I, I964, to .l. H. Leonard, and includes half-inch wide molded housing, only part II of which is shown in FIGS. 1-3. The current path through housing I0 extends from plug-in line terminal I2, terminal extension 13 to stationary contact 14 engaged by movable contact 15, through movable contact arm I6 to the upper end thereof, through a portion of cradle I7 and bimetal strip I8, through flexible braid I9 and lower terminal extension 21 to load terminal 20 having wire grip 7I mounted thereon.

Cradle I7 is pivotally mounted to housing part II on circular embossment 23 that extends into cradle aperture 99. The end of cradle 17 opposite pivot 23 is provided with opening 25 for insulating pin 26 which provides a pivotal support for intermediate latch member 27 and insulator 28. Cradle embossment 29 extends into notches 31, 32 of latch member 27 and insulator 28, respectively, to limit movement of these elements relative to cradle 17. Elongated spring element 33, constructed of relatively good electrically conducting ma-.

terial, is provided with a reverse bend at end 34 thereof. End 34 is positioned by cradle notch 35 and straddles pivot end 56 of contact arm 16, remote from movable contact 15, so as to provide additional conducting paths between contact arm 16 and cradle I7. The other end of spring element 13 is provided with notch 36 that extends into an annular groove of pin 26 to retain the latter mounted to cradle I7.

Main operating spring 37 is a wire formed tension member having its offset end 38 extending into contact arm aperture 39 and having its offset end 41 extending into aperture 42 of handle extension 40. The latter is pivotally mounted by having end 43 thereof seated at the bottom of a V-shaped notch in housing part I I. The end of extension having aperture 42 extends into a recess in arcuate portion 46 of manual operating handle 45. Arcuate handle portion 46 is positioned in arcuate housing slot 47, which guides movement of handle 45. Manually engageable part 48 of handle extends through elongated aperture 49 in the upper surface of housing 11.

Intermediate latch member 27 is engageable by latch 51, which is constituted by an out-tumed portion of modified U-shaped spring 52 that biases movable armature 53 of instantaneous magnetic trip means 55 away from its yoke 54. Load terminal extension 2ll extends between the spaced arms of yoke 54, thereby acting as a single engergizing turn for magnetic trip means 55 which is actuated when the magnitude of current flowing through circuit breaker 10 generates sufficient flux to move armature 53 to the right with respect to FIG. 1, thereby moving latch SI clear of intermediate latch 27 and permitting main operating spring 37 to pivot cradle 17 in a counterclockwise direction to its trip position of FIG. 3. For automatic time delay tripping the free inturned end 67 of bimetal 18 deflects outward until end 67 clears the plane of intermediate latch member 27 permitting the latter to pivot about pin 26 and clear latch 51.

During this movement of cradle 17 to its tripped position, the line of action of main operating spring 37 becomes positioned to the right of the contact arm pivot end 56, so that the force exerted by spring 37 pivots movable contact arm 16 in a counterclockwise direction to its tripped position of FIG. 3, established by the engagement of contact arm 16 and cradle 17 at point 57. To move cradle 17 from the tripped position of FlG. 3 to its reset or manually open position of FIG. 2, handle 45 is moved to the right from its intermediate position. During this movement projection 58 of handle extension 40 engages cradle 17, pivoting the latter clockwise until intermediate latch 31 moves below latch 51, so that latch 51 becomes effective to hold cradle 17 in its latch position of FIG. 2. During this clockwise movement of cradle 17, the engagement thereof with contact arm 16 at point 57 causes movement of contact arm 16 so that the separation between contacts 14, 15 decreases. Thus, during the closing stroke of movable contact arm 16 there will be a reduced movement of movable contact 15, whereby less kinetic energy will be developed by the time movable contact 15 engages stationary contact 14.

To operate circuit breaker from its reset or manual off position of FIG. 2 to its on position of FIG. 1, handle 45 is moved to the left with respect to FIG. 2. During the initial portion of this movement, section 59 of handle extension 40 engages contact arm offset 61 to pivot contact arm 16 in a clockwise direction. At the same time the upper end of main operating spring 37 is being moved to the left. At the point where the line of action of spring 37 moves to the left of contact arm pivot end 56, operating spring 37 brings about engagement of movable contact with stationary contact 14 to close circuit breaker 10.

In a typical construction, the separation between contacts 14, 15 during manual opening (FIG. 2) is approximately one-half inch, and for automatic tripping (FIG. 3) the separation between contacts 14, 15 is approximately three-fourths inch. This compares with a contact separation of only approximately three-eighths inch for both manual and automatic contact opening in similar prior art circuit breakers.

Thus, it is seen that the instant invention provides a novel compact contact operating mechanism that permits exceptionally large contact separation yet is constructed to limit kinetic energy buildup during contact operation during closing and normal opening operatrons.

Although there have been described preferred embodiments of this novel invention, many variations and modifications will now become apparent to those skilled in the art. Therefore, this invention is to be limitednot by the specific disclosure herein but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A circuit breaker including stationary and movable cooperating contacts, a movable contact arm to which said movable contact is mounted,

a spring-powered mechanism for opening and closing said cooperating contacts by moving said movable contact arm, latch means for maintaining said mechanism in a reset condition wherein the cooperating contacts may be closed. fault responsive means for automatically releasing latch means to trip said mechanism whereby said cooperating contacts may not be closed. operating means including a handle for selectively operating said mechanism when in said reset condition to open and close said cooperating contacts, stop means for engaging said contact arm to limit separation between said cooperating contacts when the latter are open; said stop means being operatively constructed to limit circuit opening of said contact arm to a first position when said mechanism is reset and to limit circuit opening of said contact arm to a second position when said mechanism is tripped with separation between said cooperating contacts being substantially greater when said contact arm is in said second position as compared to this separation when said contact arm is in said first position; said mechanism including a releasable cradles said stop means being carried by said cradle and being repositioned as said mechanism is tripped and reset; a stationary pivot upon which said cradle is mounted and a repositionable pivot to which one end of said contact arm is mounted; said repositionable pivot being on said cradle; said movable contact being at the other end of said contact amt.

2. A circuit breaker as set forth in claim 1 in which said operating means includes a portion controlled by said handle for moving said cradle to reset said mechanism, said handle being mounted for movement in a first direction to reset said mechanism and being mounted for movement in a second direction opposite to said first direction to close said cooperating contacts. I

3. A circuit breaker as set forth in claim 2 in which the mechanism includes an overcenter spring connected to said contact arm for moving the latter to open and close the cooperating contacts; said handle including a section engageable with said contact arm for movement of the latter toward the stationary contact; said section being operatively positioned to engage said contact arm and positively move the latter toward contact closed position before said spring is effective to move the contact arm to circuit closed position.

4. A circuit breaker as set forth in claim 1 in which contact separation of said cooperating contact is approximately 50 percent greater when said contact arm is in said tripped position as compared to said reset position.

5. A circuit breaker including stationary and movable cooperating contacts, a movable contact arm to which said movable contact is mounted,

a spring-powered mechanism for opening and closing said cooperating contacts by moving said movable contact arm, latch means for maintaining said mechanism in a reset condition wherein the cooperating contacts may be closed, fault responsive means for automatically releasing latch means to trip said mechanism whereby said cooperating contacts may not be closed, operating means including a handle for selectively operating said mechanism when in said reset condition to open and close said cooperating contacts, stop means for engaging said contact arm to limit separation between said cooperating contacts when the latter are open; said mechanism including an overcenter spring connected to said contact arm for moving the latter to open and close the cooperating contacts; said handle including a section engageable with said contact arm for movement of the latter toward the stationary contact; said section being operatively positioned to engage said contact arm and positively move the latter toward contact closed position before said spring is effective to move the contact arm to circuit closed position. 6. A circuit breaker as set forth in claim 5 in which the mechanism includes a releasable cradle; a stationary pivot upon which said cradle is mounted and a repositionable pivot to which one end of said contact arm is mounted; said movable contact being at the other end of said contact arm; said repositionable pivot being on the cradle.

7. A circuit breaker as set forth in claim 6 in which said operating means includes a portion controlled by said handle for moving said cradle to reset said mechanism. said handle being mounted for movement in a first direction to reset said mechanism and being mounted for movement in a second direction opposite to said first direction to close said cooperating contacts. 

1. A circuit breaker including stationary and movable cooperating contacts, a movable contact arm to which said movable contact is mounted, a spring-powered mechanism for opening and closing said cooperating contacts by moving said movable contact arm, latch means for maintaining said mechanism in a reset condition wherein the cooperating contacts may be closed, fault responsive means for automatically releasing latch means to trip said mechanism whereby said cooperating contacts may not be closed, operating means including a handle for selectively operating said mechanism when in said reset condition to open and close said cooperating contacts, stop means for engaging said contact arm to limit separation between said cooperating contacts when the latter are open; said stop means being operatively constructed to limit circuit opening of said contact arm to a first position when said mechanism is reset and to limit circuit opening of said contact arm to a second position when said mechanism is tripped with separation between said cooperating contacts being subStantially greater when said contact arm is in said second position as compared to this separation when said contact arm is in said first position; said mechanism including a releasable cradle; said stop means being carried by said cradle and being repositioned as said mechanism is tripped and reset; a stationary pivot upon which said cradle is mounted and a repositionable pivot to which one end of said contact arm is mounted; said repositionable pivot being on said cradle; said movable contact being at the other end of said contact arm.
 2. A circuit breaker as set forth in claim 1 in which said operating means includes a portion controlled by said handle for moving said cradle to reset said mechanism, said handle being mounted for movement in a first direction to reset said mechanism and being mounted for movement in a second direction opposite to said first direction to close said cooperating contacts.
 3. A circuit breaker as set forth in claim 2 in which the mechanism includes an overcenter spring connected to said contact arm for moving the latter to open and close the cooperating contacts; said handle including a section engageable with said contact arm for movement of the latter toward the stationary contact; said section being operatively positioned to engage said contact arm and positively move the latter toward contact closed position before said spring is effective to move the contact arm to circuit closed position.
 4. A circuit breaker as set forth in claim 1 in which contact separation of said cooperating contact is approximately 50 percent greater when said contact arm is in said tripped position as compared to said reset position.
 5. A circuit breaker including stationary and movable cooperating contacts, a movable contact arm to which said movable contact is mounted, a spring-powered mechanism for opening and closing said cooperating contacts by moving said movable contact arm, latch means for maintaining said mechanism in a reset condition wherein the cooperating contacts may be closed, fault responsive means for automatically releasing latch means to trip said mechanism whereby said cooperating contacts may not be closed, operating means including a handle for selectively operating said mechanism when in said reset condition to open and close said cooperating contacts, stop means for engaging said contact arm to limit separation between said cooperating contacts when the latter are open; said mechanism including an overcenter spring connected to said contact arm for moving the latter to open and close the cooperating contacts; said handle including a section engageable with said contact arm for movement of the latter toward the stationary contact; said section being operatively positioned to engage said contact arm and positively move the latter toward contact closed position before said spring is effective to move the contact arm to circuit closed position.
 6. A circuit breaker as set forth in claim 5 in which the mechanism includes a releasable cradle; a stationary pivot upon which said cradle is mounted and a repositionable pivot to which one end of said contact arm is mounted; said movable contact being at the other end of said contact arm; said repositionable pivot being on the cradle.
 7. A circuit breaker as set forth in claim 6 in which said operating means includes a portion controlled by said handle for moving said cradle to reset said mechanism, said handle being mounted for movement in a first direction to reset said mechanism and being mounted for movement in a second direction opposite to said first direction to close said cooperating contacts. 